A 28-year-old man has been arrested on suspicion of murdering a Lithuanian national whose body lay undiscovered for weeks.
Juozas Meilunas, 51, was found in his flat in Woodlands Court, Kettering, on 26 December after flooding in the property was reported.
Police believe the Mr Meilunas, who had lived in the town for about a year, was killed between September and November.
Detectives said he died from a head injury.
Det Ch Insp Joe Banfield, from Northamptonshire Police, said Mr Meilunas had been working for a number of employment agencies and previously lived in the area in 2013.
He said the inquiry’s focus was trying to “tie down exactly when he was last seen”.
“He would have had friends in the area and would have been known to local people, so our appeal is to anyone that knew him [to come forward],” he said.
Mr Meilunas’ body was found after a neighbour had called the fire brigade reporting the flat was flooded.
Det Ch Insp Banfield said “his body was showing signs of decomposition and he was identified via his post-mortem [examination]”.
Police said Mr Meilunas’ family were “very distressed” and that the force was supporting them, including his elderly mother, who lives in the Baltic state.